Known materials handling vehicles include a power unit, a mast assembly and an operator compartment. The mast assembly may include a plurality of mast weldments, wherein a first mast weldment may be fixed to the power unit and one or more weldments may be supported for telescoping movement relative to the other weldments. The operator compartment in a stock picker materials handling vehicle may be supported for vertical movement on the mast assembly for positioning an operator to retrieve items from shelves at elevated locations.